The invention relates to a method for controlling the electrical charging of a group of vehicles and to a corresponding control system.
The prior art discloses the practice of controlling the charging of the energy stores of a group or pool of electrically drivable vehicles by means of a control system such that requirements of the operator of the electricity grid used for charging in respect of overloads and/or overcapacities are also taken into consideration. In other words, given a corresponding requirement of the electricity grid operator, the charging of particular vehicles of the vehicle pool can be interrupted or delayed in the case of an overload in order to thereby avoid the drawing of power in the electricity grid. In an analogous manner, given a corresponding requirement of the electricity grid operator, the charging of particular vehicles of the pool can be triggered so that the excess power in the case of an overcapacity in the electricity grid is consumed completely or at least substantially by the vehicles.
In the case of the controlled charging of vehicles of a vehicle pool, charging time windows in which the vehicle-based energy store is preferably intended to be charged are often stipulated in the individual vehicles. In this case, although the charging time window is known to the control system controlling the charging of the vehicle pool, the precise time at which the vehicle begins the charging operation in the charging time window is not.
From the prior art, there are approaches that make it possible to charge vehicles of a vehicle pool by means of a cost function. The cost function stipulates the periods of time in which charging should be prioritized by means of different cost values for different periods of time 1 of the charging operation. In other words, the periods of time of a charging operation are stipulated in ascending order of the cost values. The known cost functions in this case do not take into consideration any criteria with respect to a time period with overload or overcapacity in the electricity grid or with respect to the fact that vehicle-based energy stores may be subjected to significant degradation so that at the end of the charging operation they can be charged only with a reduced power.
It is the object of the invention to control the operation of charging a group of vehicles in such a way that overcapacities in an electricity grid can be completely or at least substantially reduced efficiently by way of charging operations of vehicles from the group.
This and other objects are achieved by a method for controlling electrical charging of a group of vehicles in accordance with embodiments of the invention.
The method according to the invention serves to control the electrical charging of a group of vehicles. The respective vehicles are connected to an electricity grid for the purpose of charging a vehicle-based energy store for driving the respective vehicle. The vehicles are therefore electrically drivable vehicles, such as pure electric vehicles or hybrid vehicles, for example. In the method according to the invention, a central control system can communicate with the respective vehicles of the group and with a server of the electricity grid operator. A central control system is to be understood here as meaning a control system or a control device that controls the charging of all of the vehicles of the group. Said control system is realized, in particular, by means of software on a corresponding server. The central control system selects, based on a charging command received there, originating from the server of the electricity grid operator and specifying a (future) charging time period, a number of vehicles from the group (that is to say at least some of the vehicles of the group) that are intended to charge their vehicle-based energy stores by means of the electricity grid in the charging time period. Said selection is effected based on predetermined criteria that stipulate which vehicles are eligible for charging.
A charging time window, a departure time and a desired state of charge of the vehicle-based energy store at the departure time are respectively stipulated in advance for one or more specific vehicles of the number of vehicles and, in particular, for all of the vehicles of this number. The desired state of charge preferably corresponds to a state of charge of 100%. For a respective specific vehicle, the duration of the charging operation until the desired state of charge is reached is estimated. The estimation can be performed by the respective vehicle itself. It is likewise possible for the estimation to be carried out by the control system. In this case, the estimated charging operation (that is to say the estimated duration thereof) can be transmitted to the respective vehicle or the respective vehicle can also carry out the estimation of the charging operation itself. For the specific vehicles, the charging time period is before the departure time or ends at the departure time.
According to the invention, the respective specific vehicle distributes the (estimated) charging operation to the periods of time in ascending order of the cost values in accordance with a cost function that stipulates different cost values for different periods of time until the departure time. The respective specific vehicle is then charged in the periods of time to which the charging process has been distributed based on the cost function. In the context of the invention, a cost value represents a value on a scale for which the relationships “equal to”, “greater than” and “less than” are defined. The cost value is preferably a numerical value.
In the method according to the invention, the cost function for a respective specific vehicle is stipulated by the central control system based on the steps a) to g) described below. The designation of the individual steps with letters facilitates referencing thereto. The letters do not imply an order in which the steps are carried out.
In accordance with step a), in the case that the charging time period or a part of the charging time period is within the charging time window, a first cost value is assigned to the charging time period or to the part of the charging time period within the charging time window.
In accordance with step b), in the case that the charging time window or a part of the charging time window temporally succeeds the end of the charging time period, a second cost value, which is higher than the first cost value if a first cost value is assigned, is assigned to the charging time window or to the part of the charging time window after the end of the charging time period.
In accordance with step c), in the case that the charging time window or a part of the charging time window temporally precedes the start of the charging time window, a third cost value, which is higher than all of the assigned cost values from the set consisting of the first and second cost value, is assigned to the charging time window or to the part of the charging time window before the start of the charging time period. Here and in the subsequent text, the term “all of the assigned cost values”, always refers only to those cost values of the correspondingly defined set which were actually assigned to the periods of time when carrying out the method.
In accordance with step d), in the case that the charging time period or a part of the charging time period temporally succeeds the charging time window, a fourth cost value, which is higher than all of the assigned cost values from the set consisting of the first to third cost value, is assigned to the charging time period or to the part of the charging time period after the charging time window.
In accordance with step e), in the case that the charging time period or a part of the charging time period temporally precedes the charging time window, a fifth cost value, which is higher than all of the assigned cost values from the set consisting of the first to fourth cost value, is assigned to the charging time period or to the part of the charging time period before the charging time window.
In accordance with step f), a sixth cost value, which is higher than all of the assigned cost values from the set consisting of the first to fifth cost value, is assigned to each period of time that is neither within the charging time period nor within the charging time window and temporally succeeds the end of the charging time period.
In accordance with step g), a seventh cost value, which is higher than all of the assigned cost values from the set consisting of the first to sixth cost value, is assigned to each period of time that is neither within the charging time period nor within the charging time window and temporally precedes the start of the charging time period.
The method according to the invention has the advantage that low cost values are specified for periods of time comprising the charging time window and the charging time period. As a result of this, on the one hand, the requirements of the electricity grid operator after reduction of overcapacities and, on the other hand, the requirements of vehicle users with respect to favorable charging time windows are taken into consideration. Furthermore, using the cost function stipulated in accordance with the invention, charging at late times is also preferred, as a result of which the case that significant degradation of the energy store occurs during charging within the charging time period and as a result the requirements of the electricity grid operator to reduce overcapacities can be met only partially occurs less often. As already mentioned above, the cost values in accordance with the cost function are preferably numerical values. In a particularly preferable implementation of the method according to the invention, said values are integer and, in particular, positive values.
In a further preferred variant of the method according to the invention, the first to seventh cost values are fixedly prescribed independently of which of said cost values are assigned to periods of time. In other words, the values of the first to seventh cost values are already prescribed before the method is carried out and are no longer changed, even if only some of the cost values are allocated to corresponding periods of time. This variant of the method can be realized in a very simple manner.
In a further refinement of the method according to the invention, the assigned first to seventh cost values are stipulated depending on which of the first to seventh cost values are assigned to periods of time. This can be achieved, for example, by virtue of the fact that, although fixed possible values are prescribed for the cost values, these values are always assigned to the next higher cost value depending on the assignment to periods of time, as a result of which different first to seventh cost values result for different assignments.
In a further variant of the method according to the invention, in the case that the departure time is within the charging time window of the respective specific vehicle, the charging time window is shortened so that the departure time coincides with the end of the charging time window. Likewise, in a further variant of the method according to the invention, in the case that the time of the stipulation of the cost function is after the start of the charging time window, the charging time window is shortened in such a way that the start thereof coincides with said time.
In addition to the method described above, the invention relates to a central control system for controlling the electrical charging of a group of vehicles, wherein the respective vehicles are connected to an electricity grid for the purpose of charging a vehicle-based energy store for driving the respective vehicle. The central control system can communicate with the respective vehicles of the group and with a server of the electricity grid operator. The central control system is configured to select, based on a charging command received there, originating from the server of the electricity grid operator and specifying a charging time period, a number of vehicles from the group that are intended to charge their vehicle-based energy stores by means of the electricity grid in the charging time period. In this case, a charging time window, a departure time and a desired state of charge of the vehicle-based energy store at the departure time are respectively stipulated in advance for one or more specific vehicles of the number of vehicles, wherein, for a respective specific vehicle, there is an estimated duration of the charging operation until the desired state of charge is reached.
The respective specific vehicle distributes the charging operation to the periods of time in ascending order of the cost values in accordance with a cost function that stipulates different cost values for different periods of time until the departure time. The control system is configured to carry out a method in which the cost function for a respective specific vehicle is stipulated by the central control system in accordance with steps a) to g) of claim 1.
In a particularly preferred embodiment, the control system according to the invention is configured to carry out one or more preferred variants of the method according to the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.